Saturated Label Effects with Multi-Slice Imaging in ASL

Wayne Lee¹, Rafal Janik², Bojana Stefanovic^2,3, John G. Sled^1,3

Conventional practice for whole brain cerebral perfusion imaging using arterial spin labelling (ASL) is to acquire consecutive transverse slices from the inferior to the superior aspect of the brain. However, when consecutive slices are acquired at equivalent post-label-delay a confound associated with ascending slice order becomes evident. Labelled blood that is intravascular and transiting to a distal slice can be saturated during the imaging of proximal slices. This study demonstrates that this effect decreases label efficiency by an undetermined amount, which may lead to underestimated perfusion. This effect may be avoided by acquiring multislice data from superior-to-inferior acquisition using the Round Robin sampling approach.